Evidence suggests a weak magnetic field millions of years ago may have fueled the proliferation of life.
埃迪卡拉纪, 从6.35亿年前到5.41亿年前, 是地球历史上的关键时刻吗. 它标志着一个变革的时代，在这个时代，复杂的, 多细胞生物出现, 为生命的爆发搭建舞台.
But how did this surge of life unfold 和 what factors on 地球 may have contributed to it?
来自 澳门威尼斯人网上赌场 have uncovered compelling evidence that 地球’s magnetic field was in a highly unusual state when the macroscopic animals of the Ediacaran Period diversified 和 thrived. 他们的 澳门威尼斯人网上赌场，发表于 自然 通信 地球 & 环境, raises the question of whether these fluctuations in 地球’s ancient magnetic field led to shifts in oxygen levels that may have been crucial to the proliferation of life forms millions of years ago.
根据 约翰塔都诺小威廉·凯南. 大学教授 地球与环境科学系, one of the most remarkable life forms during the Ediacaran Period was the Ediacaran fauna. They were 以其与早期动物的相似而闻名—some even reached more than a meter (three feet) in size 和 were mobile, indicating they probably needed more oxygen compared to earlier life forms.
“Previous ideas for the appearance of the spectacular Ediacaran fauna have included genetic or ecologic driving factors, but the close timing with the ultra-low geomagnetic field motivated us to revisit environmental issues, 和, 特别是, 大气和海洋的氧合,塔都诺说, who is also the Dean of Research in the School of 艺术 & 科学s 和 the School of Engineering 和 Applied 科学s.
地球磁场之谜
约1,在我们下面800英里处, 液态铁在地球的外核搅动, 形成了地球的保护性磁场. 虽然看不见, the magnetic field is essential for life on 地球 because it shields the planet from solar wind—streams of radiation from the sun. But 地球’s magnetic field wasn’t always as strong as it is today.
Researchers have proposed that an unusually low magnetic field might have contributed to the rise of animal life. 然而, it has been challenging to examine the link because of limited data about the strength of the magnetic field during this time.
Tarduno 和 his team used innovative strategies 和 techniques to examine the strength of the magnetic field by 澳门威尼斯人网上赌场ing magnetism locked in ancient feldspar 和 pyroxene crystals from the rock anorthosite. The crystals contain magnetic particles that preserve magnetization from the time the minerals were formed. 通过测定岩石的年代, researchers can construct a timeline of the development of 地球’s magnetic field.
利用尖端的工具，包括一个CO2 laser 和 the lab’s superconducting quantum interference device (SQUID) magnetometer, the team analyzed with precision the crystals 和 the magnetism locked within.
弱磁场
他们的 data indicates that 地球’s magnetic field at times during the Ediacaran Period was the weakest field known to date—up to 30 times weaker than the magnetic field today—和 that the ultra-low field strength lasted for at least 26 million years.
弱磁场 makes it easier for charged particles from the sun to strip away lightweight atoms such as hydrogen from the atmosphere, 导致它们逃逸到太空中. 如果氢损失很大, more oxygen may remain in the atmosphere instead of reacting with hydrogen to form water vapor. These reactions can lead to a buildup of oxygen over time.
The research conducted by Tarduno 和 his team suggests that during the Ediacaran Period, the ultraweak magnetic field caused a loss of hydrogen over at least tens of millions of years. This loss may have led to increased oxygenation of the atmosphere 和 surface ocean, 使更高级的生命形式得以出现.
塔都诺和他的澳门威尼斯人网上赌场团队 之前发现的 that the geomagnetic field recovered in strength during the subsequent Cambrian Period, when most animal groups begin to appear in the fossil record, 保护磁场被重新建立, 让生命茁壮成长.
“If the extraordinarily weak field had remained after the Ediacaran, 地球 might look very different from the water-rich planet it is today: water loss might have gradually dried 地球,塔都诺说.
岩心动力学与演化
The work suggests that underst和ing planetary interiors is crucial in contemplating the potential of life beyond 地球.
“It’s fascinating to think that processes in 地球’s core could be linked ultimately to evolution,塔都诺说. “当我们考虑其他地方存在生命的可能性时, we also need to consider how the interiors of planets form 和 develop.”
This research was supported by the US National 科学 Foundation.
